Large numbers of mobile communication terminals (mobile devices, mobile stations) employed in wireless communication systems such as cellular phone systems are used simultaneously in areas where large numbers of people congregate, such as stations, shopping districts, and so on. Such areas have a much higher amount of persistent communication traffic than inactive areas, and thus it is highly possible that a large burden will be placed on a wireless base station. There are cases where, if a large burden is placed on a nearby wireless base station, mobile communication terminals are unable to carry out communication.
In addition, in facilities such as concert halls immediately following the end of an event, arrival gates at airports immediately following the arrival of an airplane, and so on, a large number of mobile communication terminals are powered on all at once. This causes a sharp increase in communication traffic, which may result in mobile communication terminals being unable to carry out communication.
In order to solve such a problem, measures are being taken whereby the number of wireless base stations is significantly increased in areas where large numbers of people congregate or areas where large numbers of mobile communication terminals are suddenly powered on.
However, a large degree of investment is necessary to install such wireless base stations, and the post-installation operations, maintenance, and so on also incur high costs. From the standpoint of environmental protection, it is desirable to aim for energy conservation, taking care so as not to increase the number of wireless base stations more than is necessary.
Furthermore, there are cases where it is difficult to secure space for increasing the number of wireless base stations in crowded areas such as city centers.
Therefore, rather than significantly increasing the number of wireless base stations, it is desirable instead to attempt to streamline communication services. Dispersing the position registrations of mobile communication terminals to multiple wireless base stations may be considered as a method to achieve such a goal.
Japanese Laid-open Patent Publication Nos. 04-213234 and 11-008878 disclose methods for causing a mobile communication terminal to select a wireless base station at the time of position registration. According to the method in Japanese Laid-open Patent Publication No. 04-213234, a mobile station (mobile communication terminal) receives broadcasting channel report information from each wireless base station, and based thereupon, selects the wireless base station with the most open channels.
According to the method in Japanese Laid-open Patent Publication No. 11-008878, a mobile station adjusts the condition of the radio signal between itself and base stations (wireless base stations) using the radio signal transmission power values of those base stations as parameters. The mobile station selects a base station based on the adjusted condition of the radio signal.
However, with conventional methods such as those disclosed in the Patent Publications described above, there is the possibility that position registrations are not effectively dispersed to multiple wireless base stations in areas where large numbers of people congregate, such as stations, shopping districts, and so on.